1. Field
Exemplary embodiments of the present invention relate to an image sensor and, more particularly, to a technology for improving a sensitivity of an image sensor.
2. Description of the Related Art
In general, an image sensor may convert an optical image into an electrical signal. The image sensor is widely used in various devices in many fields such as a digital camera, camcorder, mobile terminal, security camera, medical micro camera and so forth.
The image sensor may include a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Since the CMOS image sensor has high integration density and low power consumption, the CMOS image sensor may be implemented as an integrated circuit.
Such an image sensor may include a pixel array for sensing an optical image. Each pixel of the pixel array may include a microlens and a photo diode. The microlens may condense incident light, and the photo diode may convert light into an electrical signal.
Recently, with the development of a semiconductor technology, the size of pixels has been gradually reduced. According to the size reduction, the curvature radius of the microlens must be controlled in order to improve the light condensing efficiency.
However, since the conventional microlens has a curvature radius that is difficult to control due to process limits, the light condensing efficiency is inevitably degraded. Thus, there is a demand for new technology capable of increasing light condensing efficiency.